Rotary engine and the like



April 14, 1931. J. F. N. CRAIG ROTARY ENGINE AND THE LIKE Filed May 3, 1928 w 7 i m 2% i i g 34 3: 6

f WW Patented Apr. 14, 1931 UNITED STATES PATENT OFFICE roam raananrcx nnvmson cane, or nnoxaooan. mourn aoranr mama m TEE 1.11m

Application fled Kay 8, 1928, Serial Io. 274,888, and in Great Britain Kay 5, 1827.

This invention relates to rotary engines (the term including pumps, blowers, motors, meters and the like) of the inverted swashplate t e, that is to say, of the type wherein a plura 'ty of pistons, working in a rotary cylinder-block with their axes parallel to one another, are rotated by operative engagement with a central driving shaft or an equivalent rotating driving member in rela- 1 tion to a stationary swash-plate--a member operatively engaged with the pistons and having a cam -action thereon to move them axially of themselves in the cylinder-block as the latter, and the pistons, are rotated in relation to the said member. The invention has for its object to provide certain im rovements in rotary engines of this type. particular aim in the invention has been to provide a simple and inexpensive construction which can be applied where engines of small sizes are re uired, without involving undue loss b lea age. Moreover, the invention rovi es a suitable rotary engine for servmg either as the pump or as the metering device of the invention described in United States Patent No. 1,657,370. v

Hitherto in rotary engines of the type described, the construction has generally been one in which the driving connection between the driving shaft and the pistons to drive the latter round against the constraint of the swash-plate, has been provided by a member jointed to the shaft by means of a universal oint and pivotally engaged with the outer extremities of connecting rods, the inner extremities of which are in turn pivotally connected to the pistons.

According to one feature of the present invention, the construction in rotary engines of the type described may be considerably simplified and otherwise improved in respect of this driving connection between the driving-shaft (or equivalent part) and the pistons.

According to this feature of the invention the pistons themselves engage the swashplate, and the driving connection between the driving-shaft (or equivalent part) and the pistons, whereby the latter are moved round in relation to the swash-plate, is proplate ends of the pistons.

vided by a member which is rotatable with the shaftin a plane perpendicular thereto, and 1s shdingly engaged with the pistons. This construction is considerably sim ler than the known construction referre to above, in that it avoids the necessity for a universal joint on the driving-shaft as between the latter and the member through which the drive is transmitted to the pistons, and it avoids also the necessity of providing the pistons with connecting rods with associated end joints.

According to a further feature of the invention, the construction ma be one in which the cylinder-block provi es the aforesaid driving connection. This feature tends still further to simplify the eneral construction of the engine as it eliminates the necessity for a separate driving member (that is to say, separate from the cylinder-block) as between the drivin shaft and the swash- According to a further feature of the invention, the latter may comprise a rotary engine of the type described, and with or without either of the aforesaid features of invention, whereof the pistons themselves engage the swash-plate and are held up thereto by a retaining member which is pivoted between the pistons and extends radiall from its pivot into engagement with eac of them.

According to a still further feature, the pistons, in a rotary en ine of the type described and with or without either of the aforesaid features of invention, may themselves engage the swash-plate through the medium of a thrust-bearing interposed between the piston ends and the swash-plate and engaging the former by rubbing or rolling engagement. It is to be undertsood that the expression rubbing or rolling engagement is used to distinguish from engagement by a positive connection, such, for example, as a ball-joint between the piston ends and the thrust-bearing. As will be understood, the general construction of an engine of the type referred to may be considerably simplified by the embodiment of this feature of the invention. It is not broadly new to embody a thrust-bearing, but hitherto the pistons have been jointed to the bearing so that the latter has not been rotatable independently of the rotation of the piston in relation to the swash-plate. By avoiding, according to the invention, positive connection as between the piston ends and the thrust-bearing, an advantage accrues additional to the general advantage accruing from the provision of a thrust-bearing as between the piston ends and the swash-plate, in that any wear which may take place between the piston ends and the thrust-bearing is distributed around the engaged face of the rotatable part of the bearing and is not concentrated at one point, as it is unavoidabl in the case of piston ends jointed to the bearmg.

Preferably the retaining member aforesaid is so mounted as to be rotatable with the pistons, and conveniently it may be yieldingly controlled towards the swash-plate, for example, by a spring exerting its thrust at the p vot of the member.

According to yet another feature of the invention, the'piston ends may engage the rotating race of the thrust-bearing through the medium of ball-casters mounted upon the ends of the pistons, and preferably the ball casters comprise'each a ball mounted in a spherical bowl-shaped ball-race in the piston end through the medium of a ring of balls freely rollable therein under the said ball.

According to a further feature of the invention, the pistons may reciprocate in ballor roller-bearings interposed between them and the cylinder-block or other member connectingthe pistons with the driving shaft for rotation in relation to the swash-plate.

Other features of novelty will be apparent from the following description of concrete forms of the invention, and will be particularly claimed in the accompanying statement of claim.

Two embodiments of the invention will be described with reference to the accompany ing drawings, and it is to be understood that these articular forms of the invention are descri d purely by way of example.

In the drawings- Figure 1 is a longitudinal central section through a rotary engine according to the invention and adapted specially for use as an air-compressor.

Figure 2 is a corresponding sectional view of a smaller and lighter form of rotary engine' according to the invention adapted more e ecially for pumping liquids, and

ig. 3 is an enlarged partial sectional view illustrating a modified arrangement of the engaging parts interposed between the piston end and the swash-plate;

Fig. 4 is an elevational view of the distributing valve shown in Fig. 2, and

Fig. 5 is a sectional view of a hearing which shaft 2 to rotate therewith is a circular drumshaped cylinder block 5 bored from one end to form six cylinders 6 equally spaced in a ring concentric with the axis of the shaft 2. Sliding ineach cylinder is a piston 7, which y preferably is made as light as possible, for

example, by removing a portion of the metal therefrom as indicated at 8. The pistons are grooved as at 9 to minimize leakage of air past them. If desired, they may, how- 'ever, be fitted with piston-rings. The swashplate of the engine is constituted by a fixed ball thrust-race 10 mounted on the inner side of an inclined stationary end-plate 11, which endlate is bolted at its four corners to supporting bolts 12 extending from the valvebody 1. The pistons are operatively engaged with the swash-plate through the medium of an annular ball-bearing constituted by the cage of balls 13 and the co-operating ball thrust-race14. Each piston is provided at the swash-plate end with a centrally-disposed hemispherical projection 15 which engages with point contact the flat face of the race 14. The pistons are all-held up to the swash-plate by means of a spider-shaped retaining member 16 slidably mounted in the inner end of the central shaft 2 and springpressed by means of the spring 17 towards the swash-plate. The member 16 is pivotally mounted at its centre upon a spherical pivot 18 and its arms pass into the interior of the piston ends through slots therein and engage, at their extremities, small spherical pivots carried by, and situated inside, the piston ends concentrically with the projections 15. The spring 17 exerts its back reaction upon the end of the shaft 2.

The proportioning and disposition of parts s such that the axis of rotation of the race 14 ntersects the axis of rotation of the shaft 2 1n the plane of the outer piston-engaged face of the race 14, and the points of engagementof the extremities of the arms of the member 16 with the inside pivots of the piston ends all lie in a plane which is parallel formed at the valve-face with inlet and outlet ports 22 and 23, respectively. The inlet port 22 extends around the valve-face, along a circular line coincident with the circular path of the ports 21. Figure 4 shows a similar construction, as far as this port is concerned, as applied to the form of the invention illustrated in Figure- 2-a pum ada ted for pumping an incompressible uid. he outlet port 23, however, does not so extend around the valve face, but is of smaller area at the face than the port 22 for effective operation of the engine as an air-compressor.

As will be at once appreciated from the foregoing, the pistons reciprocate in their cylinders asthey rotate with the cylinderblock in relation to the swash-plate, and during their outward movement they draw in fluid from the port 22, and, during their inward movement, they eject the fluid through the port 23.

The cylinder-block 5 is provided around its exterior surface with air-cooling fins. The fins may, if desired, be of such formation, for example, may be spirally arranged around the cylinder-block as to take advantage of the rotation of the block in increasing the cooling effect of the fins.

In the operation of the engine, the retaining member 16 exerts thrust through the spring 17 on to the extremity of the shaft 2, and with this in view, the bearing 3 is preferably of the type which is adapted to take end thrust from the shaft 2 in the direction away from the swash-plate.

As will be appreciated, there will generally be a slight leakage from the cylinders at the valve-faces, and when operating under high pressures this leakage may set up quite an appreciable pressure upon the cylinder-block valve-face. In order to counterbalance this leakage pressure, which will be in a direction,

towards the swash-plate and will therefore tend to lift the cylinder block away from the face of the distributing valve, and, consequently, increase the extent of leakage, the ports 21 in the cylinder-block may be so dimensioned as to result in the leakage pressure being counterbalanced by the opposed pressure upon the inner end faces of the cylinders around the ports.

Referring next to that form of the invention illustrated in Figure 2, the construction is generally lighter than that of the aircompressor just described, but the general principle is the same. Thus, the engine comprises a distributing valve 30, a central rotatable shaft 31, a rotatable cylinder-block 32 bored as in the other construction to form four cylinders 33 in each of which works a piston 34. The pistons are all held up to a swash-plate constituted by a fixed ball thrustrace 35 by a spring-pressed disc-shaped retaining member 36 through the medium of an annular ball-bearing comprising a ring of balls 37 and a co-operating rotating ball race 38. As in the air-compressor, the shaft 31 is mounted in ball-bearings 39, 40. The bearing 40 1s a simple ball bearing adapted to take radial thrust. The bearin 39, however, 1s of s ial construction. %he inner race 1s shdably mounted on the shaft 31 and cooperates with a collar 71 fixed on the shaft and four set screws 72 screwed into said collar to-provide, in conjunction with the bear ng balls and the outer race 73 of the bearing, a positive stop for preventing lift of the cylinder-block away from the valveface of the distributing valve, and means, moreover, whereby the position of the cylinder-block in relation to the distributing valve may be adjusted to a nicety, for example, to take up any wear that may occur at the valvefaces. A spacing sleeve 74 is provided to position the bearings.

The rotating ,cy inder-block 32 with its pistons 34 is accommodated within a spun sheet metal casing 44 which is formed all in one piece and is obliquely recessed at 45 to take the swash-plate.

The distributing valve is a hardened steel disc formed with kidney-shaped inlet and outlet ports 48, 49 (Figure 4) so positioned at the valve-faces, as in the construction of pump illustrated in Figure 1, as to register the port 48 with those cylinders in which the pistons are moving outwardly,that is, towards the swash-plate, and the port 49 with those cylinders in which the pistons are moving inwardly. p

The pistons 34, which are of speclally light and simple construction, may comprise a tube closed at one end (the pressure end of the piston) and carrying at the other end a double-headed pin 24 mounted in the piston end in the following manner. The end of the piston tube is notched out as at 25, and the wall of the tube beyond the notch 1s pressed over onto the shank portion of the double-headed pin 24 so as firmly to grip the pin in a position in which it is coaxlal with the tube. It is found that this construction lends itself readily to ease and cheapness of manufacture.

Packing glands 7 5 are provided in the outer ends of the cylinders in the cylinder-block.

in Figure 2, the inner ends of the pistons.

should only just clear the valve face of the distributing valve as the cylinder-block rotates and the pistons reach the bottom of their stroke.

Figure 3 illustrates a refinement in respect of the operative engagement of the piston ends with the swash-plate. The point of contact of the spherical projection 15 (Figure 1) with the engaged face of the race 14 traces out a small ellipse of rubbing contact on said face and friction, of course, is set up in consequence, especially when running at high speeds and when operating under high pressures. The device shown in Figure 3 is intended to reduce this friction. It consists of a ball-caster comprising a spherical ball mounted in a bowl-shaped ball-race 51 through the medium of a ring of balls 52 freely rollable under the ball 50 in the race 51 so as to be capable of accommodatin itself in its position in the race 51 accor ing to the direction of thrust on the piston end from the swash-plate. The race 51 is formed in a plug 53 screwed in the end of thepiston 7 and a retaining cap 54 is provided to cover over the race 51. The arms of the retaining member 16 engage the interior of the piston end through the medium of a ball 55.

\Vhen workin under high pressures the lateral thrust as between the istons and the cylinder-block is very consi erable, and in order to reduce the friction from this thrust it may be desirable in some cases to interpose ballor roller-bearings between the pistons and the cylinder-block. Figure 5 illustrates a convenient arrangement for this purpose. The piston reciprocates within two spaced rings of roller-bearings 61 accommodated within a suitable cage 62 and interposed between the piston and the cylinder wall so as to be capable of rolling along said wall as the pistons reciprocate to-and-fro in the cyinder. The cylinder wall is preferably provided with a hardened metal linin 63, and the rollers, which, as shown, are slightly barrel-shaped, and of which the longitudinal curvature at the periphery of the barrel corresponds nearly to the curvature of the inner face of the lining 63, roll in longitudinal channel-shaped races formed in a sleeve 64 fitted around the piston. These races may be fiat instead of channel-shaped or may be omitted if desired. Preferably, the sleeve 64 is of hardened metal as in the case of the lining 63. The curvature of the longitudinal races formed in the sleeve 64 corresponds to the curvature of the inner face of the lining 63. The two rings of roller-bearings are spaced apart and situated towards the outer end of the cylinders, sufficient space being left, of course, behind the inner ring, to enable thepiston proper to perform its operative stroke. Stops are provided either upon the cylinder wall or upon the piston itself, to limit the movement of the rings of roller-bearings endwise of the cylinder, that is to say, to maintain the race in operative position within the annular space between the piston and the cylinder. This arrangement of piston bearings will it is advisable to re uce to a minimum the distance between the outer ring of bearings and the swash-plate.

Various modifications may, of course, be made in regard of details of construction without departing from the invention.

I claim 1. A rotary swash-plate engine, com rising, in combination, a frame having s aft,

bearings at one end and a support for a swash-plate at the opposite end, a swashplate mounted on said support, a shaft mounted in said bearings and overhanging them on that side which is towards the swashplate, a rotatable cylinder block-mounted upon the overhung portion of the shaft and having cylinder bores parallel to the axis of the shaft, a valve-face on the end of the block which is adjacent the shaft bearings, a cooperating valve face on the frame, surrounding the shaft-bearings, pistons in cylinder bores operatively engaged with the swashplate, and yielding means interposed between the pistons and the cylinder block for pressing the block against the valve face 'on tlie frame and the pistons against the swashp ate.

2. A rotary swash-plate engine comprising a cylinder block rotatably mounted and provided with cylinder bores parallel to its axis, pistons therein, a swashlate constituted by an anti-friction r01 ing contact thrust-bearing and having a plane thrustsurface facing the cylinder block, means in the pistons to engage the said plane thrustsurface with oint contact, a retaining member pivoted etween the pistons which engages each of them with point-contact to hold them against the swash-plate, the points of contact of the pistons with the retaining member all lying in a plane which is substantially parallel to the thrust-surface aforesaid, and means to press the retaining member and pistons toward the swash-plate.

3. A rotary engine comprising a cylinder block rotatably mounted and provided with cylinder bores parallel to its axis, pistons therein, a swash-plate constituted by an antifriction rolling-contact thrust-bearing and having a plane thrust-surface facing the cylinder block, means in the pistons to engage the said plane thrust-surface with point-contact, a retaining member pivoted between the pistons and engaging each of them with pointcontact to hold them against the swash-plate, the points of contact of the pistons with the neoaaee retaining member all lying in a plane which is substantially parallel to the thrust-surface aforesaid, and means to press the retaining member and pistons toward the swash-plate, it said first named means comprising a concave hall race mounted in the end of said piston halls supported in said race, and a ball intei-- posed hetween said first named halls and the plane thrustsnz face of said thrust hearing. l t. A rotary swash-plate engine comprising; an overhung shaft, hearings therefor e eyiinder-hloch mounted on the overhung POE"- tlOll of the shaft and having an end face adjacent the said hearings constituting a valve lll face for the block, cylinder horse in the block parallel to its axis, pistons therein, a swashplate constituted by an anti-friction rollingeontact thrust-hearing and having a plane thrust-surface facing the cylinder block, he means in the pistons to engage said plane thrust-surface with point-contact, a retaining member pivoted between the pistons and engaging each of them with point-contact to hold them against the swash-plate, the points of contact of the pistons with the retaining member all lying in a plane which is substantially parallel to the thrust-surface aforesaid, and means to press the retaining member and pistons towards the swash-plate. in testimony whereof I aifix my signature,

.lOllN FREDERICK NEVINSON (IRMG. 

